Endoplasmic reticulum targeted GFP reveals ER organization in tobacco NT-1 cells during cell division

Abstract

The endoplasmic reticulum (ER) of plant cells undergoes a drastic reorganization during cell division. In tobacco NT-1 cells that stably express a GFP construct targeted to the ER, we have mapped the reorganization of ER that occurs during mitosis and cytokinesis with confocal laser scanning microscopy. During division, the ER and nuclear envelope do not vesiculate. Instead, tubules of ER accumulate around the chromosomes after the nuclear envelope breaks down, with these tubules aligning parallel to the microtubules of the mitotic spindle. In cytokinesis, the phragmoplast is particularly rich in ER, and the transnuclear channels and invaginations present in many interphase cells appear to develop from ER tubules trapped in the developing phragmoplast. Drug studies, using oryzalin and latrunculin to disrupt the microtubules and actin microfilaments respectively, demonstrate that during division, the arrangement of ER is controlled by microtubules and not by actin, which is the reverse of the situation in interphase cells.

The induction of a nucleoplasmic reticulum by prelamin A accumulation requires CTP:phosphocholine cytidylyltransferase-α

“…This would result in chromatin-bound ER and/or NE cisternae becoming trapped in the interstitial space giving the impression of NR development (Gupton et al, 2006). However, it has been shown that NR can develop without mitosis (Fischer et al, 2003), persist throughout interphase (Fricker et al, 1997b;Olins and Olins, 2009) and specific cell types display heritable patterns (Fricker et al, 1997b), which strongly suggests physiological regulation.…”

Breaking up is hard to do – membrane traffic in cytokinesis

“…Tubules of ER were observed to accumulate around the chromosomes after nuclear-envelope breakdown, with the tubules aligned parallel to the microtubules of the mitotic spindle. In cytokinesis, the phragmoplast becomes enriched in ER, and this redistribution appears to be microtubule dependent (Gupton et al, 2006). Similarly, in mammalian cells, the ER is aligned around the contours of the spindle body and oriented along microtubules (McCullough and Lucocq, 2005) (Fig.…”

“…Recent studies have also hinted at a role for the ER in cytokinesis. Studies that used GFP-tagged ER-resident proteins in plant cells have revealed that the ER undergoes pronounced reorganisation during mitosis and cytokinesis (Gupton et al, 2006). Tubules of ER were observed to accumulate around the chromosomes after nuclear-envelope breakdown, with the tubules aligned parallel to the microtubules of the mitotic spindle.…”

Movement and Remodeling of the Endoplasmic Reticulum in Nondividing Cells of Tobacco Leaves

“…We should caution, however, that this by no means excludes a role for microtubules exerting a regulating influence on the dynamics of the ER at other stages of the cell cycle. Indeed, it is quite likely that during the transition to metaphase, while the nuclear envelope resorbs into the ER, which then forms aggregates at the spindle poles, there is a switch over from an actin-based movement to microtubule-based movement on spindle microtubules (Gupton et al, 2006). The association of ER membrane with spindle microtubules in plants is well established (Hepler and Wolniak, 1984).…”